Modern theologians attuned to the realities of poverty have usually kept their distance from classical Christian affirmations of voluntary poverty. They have been concerned, for good reason, that such affirmations romanticize or even reinforce material deprivation and exploitative social arrangements. My dissertation develops an account of voluntary poverty as an egalitarian political practice in a way cognizant of those concerns, drawing on the poverty movements of the twelfth and thirteenth centuries. Although those movements do in some ways confirm our worries about voluntary poverty, I also recover from them a way of thinking about voluntary poverty that is sensitive to the complex relationship between poverty and social power. This dissertation has five chapters. In the first chapter, I argue that the decisive shift between the classical Roman and early Christian economic imagination had to do with the appearance of 'the poor' as a social class. This shift had some radical consequences, but 'the poor' who appeared were still defined by their passive dependence on broader society. The shock and challenge of the twelfth-century social movements describing themselves as 'the poor of Christ,' who I introduce in chapter two, was that they represented themselves an active and contentious poor, blurring the boundaries between themselves and 'the poor' more broadly construed. In the third chapter, I argue that Francis is best understood as an heir to these earlier movements. Their concerns are an extremely important hermeneutical key to Francis's writings. While many of the earlier movements had been judged heretical, Francis worked to articulate their vision of the apostolic life in an orthodox frame. But the result, I argue, was ambiguous: his vision of poverty provides resources both for a critique of certain mainstream practices and for undermining the movements' challenge. In the fourth and fifth chapters, I show how later Franciscans continued to wrestle with the key political contentions of the earlier movements. In chapter four, I focus on the question of social inclusion and participation in conversation with Clare of Assisi. In chapter five, I turn to the question of spiritual and ecclesiastical authority in conversation with Bonaventure.